Manufacture of rubber vulcanization accelerators



Patented Oct. 28, 1930 UNITED STATES PATENT OFFICE A 'WINFIELD SCOTT, OF AKRON, OHIO, ASSIGNOR TO THE RUBBER SERVICE LABORA- TOBIES COMPANY, OF AKRON, OHIO, A CORPORATION OF OHIO MANUFACTURE or RUBBER vnmamzn'rrou ACCELERATOBS No Drawing. Original application filed October 9, 1925, Serial No. 61,587. Divided and this application filed March 2, 1927. Serial No. 172,200.

The present invention relates to the manufacture of organic salts of mercaptan compounds and particularly to the manufacture of the reaction product of a mercapto-arylw ll thiazole andlike compounds with a fully saturated organic base such as saturated aliphatic amines and the like. Such fully saturated compounds are of the type wherein no two atoms present in the compound .are

v linked or joined together by more than one mula osn

is one of the reaction products obtained by heating a mixture of thiocarbanilid and sulphur. I, have found that the usefulness of this compound and all analogous materials as accelerators in the rubber vulcanization process can be greatly increased by reacting such ompounds wit organic bases of the type hereinafter described to produce organic salts and using the material so obtained as vulcanizationaccelerators.

- Mercapto compounds are somewhat acidic in nature due to the resence of the -SH oup contained therem, and will, therefore, orm salts of various metals, such as sodium, zinc, lead and the like, andwill also react with .the more stable and less volatile of the or anic bases to form compounds which may be termed organic salts. These organic salts possess particularly valuable characteristics as accelerators of the rubber vulcanization process as has been set forth in my earlier application referred to. The present application is concerned with the manufacture ofthe reaction products of mercaptans with bases, whereby the mercaptan is sotreated as to decrease its natural acidity or conversely to increase its basicity.

Various types of fully saturated organic materials may be employed to decrease the acidic nature of mercapto compounds. One preferred type of materials employed for the object set forth comprises the fully saturated organic condensation prodlicts of ammonia, that is, fully saturated compounds produced by the direct union of an organic compound such as an aliphatic aldehyde with ammonia,

either by condensation or by addition reac-' tions. The aldehyde ammonia reaction products, although not very strongly basic of themse1ves,will react with aromatic mercapto compounds and particularly with the mercapto-thiazole derivatives to produce compounds having desirable vulcanization accelerating properties. Hexa-methylene-tetramine (CH .N for example, reacts slowly with mercapto-benzo-thiazole at temperatures ranging from 140 to 225 C. to produce a dark, resinous product. At temperatures somewhat above 225 C., decomposition of.

the material is liable to occur, accompanied by the evolution of substantial quantities of gases, such as h drogen sulphide, thereby producing a hard, terial having impaired accelerating value.

One method of preparing a reaction product possessing desirable properties for the object desired, comprises heating a mixture of approximately 140 parts hexa-methylenetetramine (dry or in aqueous solution, as preferred), with approximately 165 parts of mercapto-benzo-thiazole at a temperature of 150 C. orthereabjout, for approximately an hour, during which time a reaction takes place. After the initial reaction is over, the mixture is. heated to about 200 C. and'ma'intained thereat fora period of about four hours, whereupon, after cooling, a dark, resicarbonized resinous manous product is obtained which can be ground'to a dark brown powder.

Other means of carrying out the reaction described abovemay, of course, be employed.

' Thus, in place of hexa-methylene-tetramine in crystalline form, I have used an aqueous solution thereof, prepared, for example, by

saturating the necessary quantity of comportions of the reacting ingredients mayv also be employed than those mentioned above. Thus, instead of reacting equi-molecular parts of the materials as shown, I have combined one proportion of hexa-methylene-tetramine with one, two and three molecular proportions of the mercaptan.

Other bases than those set forth have been made and combined advantageously with a mercaptan to prepare compounds of the type mentioned, and which possess desirable vulcanization accelerating characteristics. Thus, as examples of such bases, I may em ploy fully saturated organic bases, that is, bases containing within the molecule no two atoms joined to one another by more than a single bond or valence. Such bases are necessarily of the aliphatic series of compounds.

and comprise the organic ammonium derivatives such as tetra-methyl-ammonium hydroxide N(CH,) .OH and like compounds, primary and secondary amines such as piperidine and the like, secondary di-amines, for example, piperazine cmom tri-methyl-sulphonium hydroxide (OIL-Q S.OH, as well as other organic compoundspossessing basic properties.

Furthermore, it is to be understood that while I have specifically mentioned mercapto-benzo-thiazole as'an example of-a mercaptan, other. compounds may, as I have found, be used successfully for the prepara-v tion of my preferred type of accelerators.

Thus, I may use, as a mercaptan compound, the aliphatic mercaptans such as eth 1 mercaptan, butyl mercaptan, and the li e, aromatic mercaptans, such as thio-phenol, thiocresol and the like; benzo-thiazole mercaptans and substitution products thereof; such as mercapto-tolyl-thiazole, the naphthy-lthiazole mercaptans; thio-oxy-indole caband substitution products thereof; amidothio-phenols and derivatives; 2-mercaptothiazolin car-s and derivatives the thio-anilides rn Oaks-cm;

2-mercapto-benzimid-azol; mercapto-iminathe thio-amides, such as thio-ammelin sn N N mai I JLNH,

that is mercapto compounds of the aliphatic and aromatic series. a

' My invention then, covers broadly the manufacture of reaction roducts of atype particularly useful as ru ber vulcanization accelerators, which products are formed b the reaction of saturated organic .bases wit ries containing the SH grouping, that is, the mercaptans and mercaptan derivatives. The invention is to be understood as not limited to the exact procedure followed or proportions employed in the foregoing examples, which are illustrative only and not limitative of my invention. Moreover, the invention is to be considered as not limited by. any theories advanced in explanation of the chemical changes involved in the manufacture of the compounds set forth but is limited solely by theclaims attached hereto as a part of this specification wherein I intend to claim all novelty inherent in' my invention as is permissible in view of the prior art.

WhatI claim is:

1. The process of manufacturing an organic salt of a mercaptan which comprises heating a mercaptan with a fully saturated organic condensation product of ammonia at a temperature below the decomposition point of the materials. v

2. The process of manufacturing a mer-v captan -derivative which comprises heating, a compound containing the I group with a fully saturated organic base.

3. The process of manufacturing a mer captan derivative which comprises heating a mercapto-aryl-thiazole compound with an equi-molecular proportion of a .fully satucompounds of the'aromatic or aliphatic sei rated organic condensation product of ammonia. a

4. The process of manufacturing a mercaptan derivative which comprises heating mercapto-benzo-thiazole with from to 1 molecular equivalents of hexa-methylene-tet ramine.

5. As a new product the mercaptan derivative comprising the reaction product'of a mercaptan with a fully saturated organic condensation product of ammonia.

6. As a new product the mercaptan derivative comprising the reaction product of a mercapto-aryl-thiazole compound with an equi-molecular proportion of a fully saturated organic condensation product of ammonia.

7 As a new product the mercaptan derivative comprising the reaction product of mercapto-benzo-thiazole with from to 1 molecular equivalents of hexa-methylene-tetramine. I

8. As a new product the mercaptan derivative comprising the reaction product of a compound containing the 250s]; group witha fully saturated organic base. In testimony whereof I afii'x 'my signature.

WINFIELD SCOTT. 

